The use of heaters to heat water in narrowboats, which water is used for both potable and zone heating purposes is, of course, well known. Typically, the known installation consists of an auxiliary heater which uses diesel fuel similar or the same as that used by the prime mover or engine used to power the narrowboat. The auxiliary heater includes a burner which heats water circulating through the heater within a water jacket. The heated water is then circulated through a potable water tank where heat exchange takes place to heat the potable water within the tank. The heated potable water within the water tank is then used for potable purposes such as washing and cooking.
In addition to the heating of the potable water within the hot water tank by the auxiliary heater, the water is also heated by a hot water circuit emanating from the diesel engine used to power the narrowboat. In the event that the diesel motor is not operating, then the auxiliary heater may be used alone. When the diesel engine is operating, the auxiliary heater may be manually shut down thereby conserving energy and reducing operating noise.
The known system also uses a water circuit running from the auxiliary heater to heating zones of living space on the narrowboat. These zones are heated typically using a radiator type heater. Water from the auxiliary heater is circulated through the heater and this heater then heats the zones. When the temperature of the zone reaches a comfortable value, the operation of the auxiliary heater is then terminated by way of a manual shut off valve and, thereafter, flow is similarly initiated.
There are inherent disadvantages with the systems presently in use and described above. First, there is no provision for obtaining potable water from the heated water tank at a preferred temperature. The temperature of the potable water within the tank is heated by the auxiliary and/or the engine water circuit and there is no control over the temperature of the water to be used for potable purposes. The only control of the water temperature is that if the water in the auxiliary heater becomes too hot, the auxiliary heater will terminate operation. If the temperature of the water in the cooling circuit of the prime mover becomes too hot, there likewise is a fail-safe provision to shut down the engine. But these controls are independent of the water temperature within the potable water tank.
A second disadvantage of the present system is that there is likewise little or no automatic control over the temperature of a zone within the narrowboat which zone is heated by water circulating from the auxiliary heater. In the event the zone temperature becomes too hot, a manual valve is used to terminate and initiate hot water flow through a radiator in the zone of interest.
A third disadvantage of the present system is that there is no provision for automatically shutting off the auxiliary heater when the diesel engine used to power the narrowboat is also operating. Thus, both the auxiliary heater and the diesel engine are being used to heat the potable water and there may be no need to do so if the potable water has reached its desired temperature. This is inefficient and costly and it produces unnecessary noise.
Yet a further disadvantage of the present system relates to the air intake and exhaust outlet associated with the auxiliary heater. The exhaust outlet and the air intake are typically incorporated in a single fitting which fitting was mounted on the side of the narrowboat. The heater exhaust exited from the center of the fitting with inlet air for the heater being inletted about the outer area of the fitting surrounding the inlet. Normally, this is sufficient to avoid contamination of the inlet air. However, narrowboats are often moored next to the wall of a canal or next to a second and adjacent narrowboat. It has been found that the oxygen depleted exhaust from the engine was being inhaled into the engine through the air intake in the fitting. The lack of oxygen resulted in a weak or non-existent combustion of fuel by the burner which resulted in flame outs and inefficient oxygen and air use by the auxiliary heater.